Coffee may be ok, but coffee drinkers not living longer

Java drinkers tend to smoke, get less exercise, and have other bad habits.

Is coffee good or bad for you? If you follow the medical literature, you might think that the answer changes a few times a year. Different studies have found associations with various ailments, while others suggested that people who hit the java actually outlived their peers.

Now, a new study is out that not only finds that coffee has a positive effect, but may help explain why the earlier studies were so confused. As it turns out, coffee drinking is associated with a broad range of bad habits (most notably smoking), so if one adjusts the numbers to compensate for those, coffee drinking starts to look pretty good. Before you rush off for your latest hit, however, you should note the biggest limitation of this study: its population was recruited exclusively from the AARP. If you're not considering retirement, you might want to hold off until we see more from a study with a younger demographic.

AARP (American Association of Retired Persons) membership is open to anyone over 50, so the population at the start of the study was between 50 and 71. On the plus side, it was huge: over 400,000 individuals. And that was after the authors got rid of people who already had cancer, heart disease, and/or strokes. The initial survey included questions about coffee consumption along with a lot of other health and dietary habits. Once enrolled, the authors followed the participants for 12 years, or until Social Security records indicated they had died.

At first glance, things didn't look good for coffee, as those who partook seemed to have elevated risk of death. But as the authors worked through the numbers, it became clear that java ingestion was associated with some bad habits. Well, a lot of bad habits: "coffee drinkers were more likely to smoke cigarettes and consume more than three alcoholic drinks per day, and they consumed more red meat. Coffee drinkers also tended to have a lower level of education; were less likely to engage in vigorous physical activity; and reported lower levels of consumption of fruits, vegetables, and white meat."

The authors built a statistical model that could compensate for all of these factors and ran a series of tests to determine whether coffee intake had a significant effect on survival. In fact, once they divided up the population accurding the the degree of ingestion—five groups, ranging from less than a cup up to over six a day—they were running so many tests that they candidly admit that "Several differences (P<0.05) would be expected by chance alone."

But the pattern they saw suggests chance wasn't an issue. As coffee dose increased, the survival of both men and women went up. With intake of two or three cups daily, mortality had dropped by roughly 10 percent, and stayed there as consumption went up further (the effect was slightly more pronounced in women).

What's going on? Many studies that saw risk with coffee have suggested that its stimulant effect would have an impact on those specifically prone to heart disease. But the survey had registered preference for decaf or full strength, and it didn't make any difference. But a proposed mechanism for positive effects also failed to hold up. Coffeee is loaded with antioxidants, which have been suggested to reduce the sort of cellular damage that can lead to cancer. Out of the various causes of death the authors looked at, however, cancer was about the only one that didn't drop as coffee intake went up. And the authors looked at a variety of causes: "heart disease, respiratory disease, stroke, injuries and accidents, diabetes, and infections."

(Maybe the caffeine helps in the accidental deaths department?)

The fact that just about every possible cause of death sees an effect from coffee would be the primary reason to view this study skeptically. There are a a few others, mostly noted by the authors themselves: the coffee drinking (and other habits) were all self-reported, and were just checked at the start of the study. And, as always with studies of this sort, the authors controlled for all the obvious factors that are known to influence mortality, but they can't control for everything (in part because we don't know everything).

But there are also a few reasons to take this seriously. A number of other recent studies have seen a similar impact on mortality in coffee drinkers, and most of those have involved a substantially younger population, so the effect isn't simply limited to prolonging the lives of older individuals. In addition, the apparent dose-dependence argues that there is a real effect here.

Ultimately, what we'd really like to see to make sense of this is a mechanism that explains coffee's impact, but we may find out there isn't one—instead, there are probably a number, since it seems to influence many causes of death. In addition, as the authors of this study note, there are over 1,000 compounds in a typical brew of coffee, and figuring out which does what biologically will not be a simple thing.

In the meantime, though, you can probably drink up. Just make sure you don't have a cigarette and bacon cheeseburger with it so you can avoid undercutting any of the benefits seen in this study.

Lower risk of death? I think that risk is 100% for all living persons and is not reduced by coffee or anything else. Maybe lower risk of *premature* death, or death by [insert cause here]? Or maybe just change the title to "Coffee associated with higher longevity"?

I can't see the full article, but I'd be curious if they controlled at all for brewing method. My understanding is that while it's generally the same, certain classes of brewing methods can result in significant changes in a few major compounds in coffee. The big one that comes to mind is cafestol, which at least some studies indicate can have a significant effect on cholesterol levels. It is present in significant quantities in a typical bean, and thus appears in significant quantities in unfiltered coffee. But because it strongly binds to paper it's barely present at all in any filtered coffee.

I don't know much about the overall chemistry of coffee, but it is complex and there are a lot of ways to make it, so I wonder if that has any longer term effect.

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The fact that just about every possible cause of death sees an effect from coffee would be the primary reason to view this study skeptically.

Is it? Caffeine is a mild but pretty broad stimulant isn't it (plus there's the piles of other stuff in coffee)? At least on the face of it constant consumption of something that messes with the CNS seems like it could have a pretty wide spectrum of effects.

As the saying goes, there are lies, damned lies, and then statistics. I'm well into the demographic tested here, and first of all I will authoritatively claim that the mortality rate for human beings is 100%...

But, look...if you do this:

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And that was after the authors got rid of people who already had cancer, heart disease, and/or strokes.

...if you remove the people who are sick from the study, wouldn't you automatically--no coffee needed--see a downturn in the "mortality rate" within the age group studied? Seems like you would.

I guess I'm a bit jaded, because over the years I've seen a certain phenomenon repeat itself. It will vicariously "be revealed" from time to time that a certain vitamin, mineral, or food that people usually take for granted has near-miraculous healing/longevity properties that "have only now just been discovered." I remember same for Vitamin C supplements. Now it is Vitamin D supplements (never mind that just taking off your shirt for 15 minutes a day in the summer will provide your body with > 20,000 IUs of Vitamin D, far more than the currently "recommended" dose of 1k-2k iu's daily.) The RDA for vitamin D is still 400IU's, I believe. But whether it is milk, coffee, or some food or vitamin or mineral supplement (can anyone forget the "miracle" of chromium picolinate?) it all looks to me like simple marketing. Convince people that something has near-miraculous effects and people will consume that product in near-miraculous numbers. I've seen it all before. It's eerie--almost haunting.

I can't see the full article, but I'd be curious if they controlled at all for brewing method. My understanding is that while it's generally the same, certain classes of brewing methods can result in significant changes in a few major compounds in coffee. The big one that comes to mind is cafestol, which at least some studies indicate can have a significant effect on cholesterol levels. It is present in significant quantities in a typical bean, and thus appears in significant quantities in unfiltered coffee. But because it strongly binds to paper it's barely present at all in any filtered coffee.

I would amend this to say 'any paper-filtered coffee.' There are wire-mesh filters available for drip machines. And the wire mesh, supposedly, leaves some of the more complex flavors in the coffee as well.

I wonder if they accounted for socioeconomic status. People who have the time and money to be sitting around drinking coffee all day probably also have better access to health care, less stress, etc. Not exactly the causal mechanism we're all hoping for.

Coffee consumption was assessed by self-report at a single time point and may not reflect long-term patterns of consumption. The distinction between persons who drank caffeinated coffee and those who drank decaffeinated coffee was subject to misclassification, since these categories were defined on the basis of consumption of either beverage more than half the time.

I don't see how you can make such bold statements about coffee when you don't even know how much coffee your subjects are drinking other than at baseline.Also, the charts they show is for 4+ cups of coffee. Who the hell drinks 4+ cups a day?What about 2+ cups a day when adjusted for all the various lifestyle factors?I'm not a statistician or a scientist but I work in the field peripherally and I'm not sold on this study.

I and lots of people I know drink 4+ cups of coffee every day. In the coffee industry, a 'cup' is actually 6 oz (I guess to account for adding cream?).

Anyhow, studies like this are generally quite useless -- in fact, epidemiology in general is basically a waste of time. I find it ironic that they point to red meat consumption as increasing risk, because that assumption itself is based on BS epidemiology studies. A 10% change in risk is a 0.1 fold difference -- no real scientist would take an effect of that strength seriously.

And that was after the authors got rid of people who already had cancer, heart disease, and/or strokes.

...if you remove the people who are sick from the study, wouldn't you automatically--no coffee needed--see a downturn in the "mortality rate" within the age group studied? Seems like you would.

No, because the non-coffee drinkers with those illnesses were also excluded.

Actually if you start with old people and exclude the sick (and obviously, the already dead), you ignore the possibility that Coffee might actually be increasing the incidence of early illness/death, weeding out the weak before they make the study.

While the weak abstainers survive long enough to make it into the study and skew the results to the exact opposite of what is actually happening.

Articles like this (as interesting a read as it is) are the reason I do not give a damn about most "Product X is good/bad for you statements. You need to eat/drink/smear grass/some exotic berries/crushed dung beetles to live longer and healthier ...

Most of the time with some hypothetical scientific sounding explanation like "High in anti-oxidants" anti-oxidants are quickly becoming the snake oil of the 21 century.

In the end it seems to come down to embarrassingly common sense answers each and every time. Go outside and exercise, eat your greens. Your grandmother could have given these tips to you. You wouldn't need a horde of scientists for that.

And it makes sense. Evolution is a pretty masterful engineer, it would be really weird if our well-being would depend or be hugely impacted on a single factor or food item. Our body needs a couple of things to work well, but it seems pretty flexible in the amounts and how it gets them and sometimes it can take stuff and transform it.

The fact that just about every possible cause of death sees an effect from coffee would be the primary reason to view this study skeptically.

Is it? Caffeine is a mild but pretty broad stimulant isn't it (plus there's the piles of other stuff in coffee)? At least on the face of it constant consumption of something that messes with the CNS seems like it could have a pretty wide spectrum of effects.

The big problem with most of these kind of studies is that they often "prove" all sorts of things. I could do a test of every food and probably find some correlation between not being hit by a bus and eating asparagus. No one would publish that though.

When one thing winds up saying it reduces the risk of near everything, things get a little questionable unless there is a really good reason for it. It sounds like their model might be a bit off, remember they're trying to adjust for all the bad things people eat and that's not easy to do. But more importantly, how do you adjust for a handful of bad things and not everything? It's associated with a handful of other vices, but that's probably not the extent of it and it's not universal.

It's one of those things where it's doing too much without telling us anything at all (this isn't saying "drink coffee to live longer" it's saying "people who drink coffee at an old age live longer". It could just be they drink coffee because they're active people and that activity helps you live longer).

I and lots of people I know drink 4+ cups of coffee every day. In the coffee industry, a 'cup' is actually 6 oz (I guess to account for adding cream?).

Anyhow, studies like this are generally quite useless -- in fact, epidemiology in general is basically a waste of time. I find it ironic that they point to red meat consumption as increasing risk, because that assumption itself is based on BS epidemiology studies. A 10% change in risk is a 0.1 fold difference -- no real scientist would take an effect of that strength seriously.

Again with respect to 4+ servings my data shows that it is uncommon (<10%). It is self reported data as well for thousands of subjects.I think you would be throwing out the baby with the bathwater if you reject all epidemiology. As I mentioned above, I am not a fan of this study because the coffee servings were only reported ONCE at the start (baseline). There was no followup tracking of caffeine, exercise, smoking, drinking,etc.

I and lots of people I know drink 4+ cups of coffee every day. In the coffee industry, a 'cup' is actually 6 oz (I guess to account for adding cream?).

Anyhow, studies like this are generally quite useless -- in fact, epidemiology in general is basically a waste of time. I find it ironic that they point to red meat consumption as increasing risk, because that assumption itself is based on BS epidemiology studies. A 10% change in risk is a 0.1 fold difference -- no real scientist would take an effect of that strength seriously.

With a very large sample size, 10% is pretty impressive, especially considering this is just something that a lot of people do. This isn't a drug in a trial here, this is coffee. How useless would this be if they found that coffee decreased lifespan even with taking cigarettes into account? What if they had found that coffee improved survival by 100%? Would it be useless then? Should everyone ask a psychic to tell them what their results will be prior to doing a study so that they don't risk finding out something that is a "waste of time"? Besides, 10% might not be much if one could be 10% more alive, but alive is a binary state, so its really a 10% better chance of being alive rather than being dead.

The problem with this kind of study is this: if you have 5 "bad habits" and you have epidemiological data to compensate for each habits, then you are almost guaranteed that if you remove the 5 habits that whatever you are studying will look good if what you were stuying occurs more frequently with the bad habits.

The reason is simple: almost always "bad habits" are dependant of each other. Therefore when you compensate for lets say habit A and B by adding the risks A+B, you are overcompensating the risk because because when their risk are calculated, you always have one risk contaminating the other by being associated with the other.

To be more clear, let's show it by going to the extreme: suppose (for the understanding of the principle) that there were a 100% association with smoking and alcoolism (both ways - that is that all smokers would be alcoolic and vice versa). Say you find in separate studies that smokers have their mortality 10% higher and in another study that alcoolics have their mortaility 10% higher. If you compensate for both you would erroneously reduce your data by 20%, while the correct value is only 10% (because of the 100% association between the two). Now, if what you are studying had in reality no effect and was always associated with the bad habits: then the group with the bad habits were expected to have 20% higher mortaility 20% but only got 10% higher (for the reason explained above), so you would think that what you are studying had a protective effect that reduced by 10% expected mortality, and that would totally false.

You would think that studies would correct for all the interaction of factors (like these bad habits) adequately, but in practice is almost impossible to do (with only 5 habits you already have 2^5=32 different interactions!) because data soon become insufficient to perform all those possible interactions.